Making and Breaking Bonds

A chemical reaction is when substances (called reactants) change into new substances (called products). During this process, chemical bonds are broken and new ones are formed.

Writing Chemical Equations

Chemists use equations to show what happens in a reaction. For example, when hydrogen and oxygen make water:

\[ 2H_2 + O_2 \rightarrow 2H_2O \]

The arrow shows the direction of the reaction, from reactants to products.

Types of Chemical Reactions

• Combination: Two or more substances join to form one (e.g., iron and oxygen make rust).
• Decomposition: One substance breaks apart (e.g., water splitting into hydrogen and oxygen).
• Replacement: Elements switch places (e.g., zinc and hydrochloric acid make zinc chloride and hydrogen).

Chemical reactions are everywhere—from baking bread to powering cars!